Hi:

    Before one gets his knickers in a knot by the title of the post, I am asking about the minimum amount of castor in a blend of oil to prevent damage caused by a lean run in the old style engines with c.i. and steel p&c with bushings in the crankcase.  There are times, for some reason, an engine will be run in a very lean flight. Stuff happens!

    I have really fried a couple of O.S. plain bearing circa 1960-70 stunt engines and they are still are one flip starting engines.  I also never damaged a Fox .35 Stunt after very hot and lean Foxberg runs.  Perhaps, it was due to fuels having about 27% castor for lube.  I was told many years ago, that it is difficult to ruin  an engine by running it with a very high percentage castor oil mix.  To this date, I have found this to be true.  The inside and outside of the engine turned a very dark brown but there appeared to be no damage to the engines.

    Now to the meat of the question.  I have ringed engines that have iron and steel p&c combination and some with steel cylinders with a ringed aluminum piston.  Can I mix something like 13% castor,11% synthetic, 7% nitro. 2% prop and the remainder alky to use in all engines safely?  A friend of mine has been running 11% castor, 11% synthetic in all of his engines for 40 years, and has never had a problem.  Perhaps he has ben lucky.  I am attempting to avoid having to have two mixes for flying.

     Yes, I have read Randy's notes re. engine fuels. If I have to have two mixes, then so be it.  One thing else, I have changed to using the Metric System for mixing fuels and have found it to be vastly superior to using the "American" method of measurement.  "Try it, you will like it."

                                                                                                    Have a great day,

                                                                                                    Frank McCune

Depends on the weather .

the QUALITY is as important as the QUANTITY .

    Hi MM:

    What makes propylene oxide dangerous?


                                                                                                Take care,

                                                                                                Frank McCune

I have several PA65's and several RO Jett's of various sizes.  I have never run more than 20% total oil with at most 5% castor in any of them.

They all stay very clean inside except for the slight brown coating on the top of the piston that needs to be cleaned off about ever 200 flights or so.  This is probably due to dirt more than anything else.

I have one PA65 that has between 600 and 700 flights on it using 12 to 20% nitro and 20% total oil with 17% Klotz and 3% castor.  It still pops like it was new and runs very, very well!  Except for the occasional cleaning of the top of the piston it has needed no replacement or repair and the inside of the engine is clean and shows no visible wear!

I fly mostly in Tucson AZ where the temperatures sometimes reach 110 degrees or more (the reason for the nitro increase in summer) and do not have any problems with these engines!

Randy Cuberly

Frank: I run ALL my 2 stroke engines on 10% nitro, 22 or 23% oil, 50/50 castor/synthetic.

This includes both ringed and lapped piston engines from as far back as the EARLY 50s.
Fox, Johnson, Atwood Triumph (ringed), McCoy (both ringed and lapped) and VECO.

I have NEVER experienced a failure, even after some screaming lean runs.

Bob Z.